I've had that and have also read about a lot of people who get that. Just a few nights ago, I felt my body almost jerk as I was falling asleep, unsettling thing, but I knew it was muscle tension trying to let go. That falling asleep and suddenly lurching awake happens when a person hasn't been sleeping well enough to get their REM or dream sleep, and when a person is exhausted and very tired, and also usually under a lot of stress. It's a natural thing for the body to jerk like that just as you fall asleep, it's the muscles in extreme need of relaxation, the mind swirling like you're going to pass out, and this huge release wakes you up with a big spasm. It's a scary and uncomfortable feeling.
Try to decide what's stressing you out and try to minimize the problem, exercise and eat well and drink plenty of water daily, and get enough good, solid sleep. I know, sometimes it's hard in our busy world to relax, but the more a person is busy, the more they need their sleep. I might add that if you find you have trouble going to sleep sometimes because you're so worked up, just take a couple Tylenol PM, and you'll for sure get some good rest. But if you want that big jerk-awake to stop, you must rein in your lifestyle, exercise to release tension in your body, and if you have to go to bed at 9 pm to get up at 6 am, then do it. I always miss my 10:00 pm shows because I need a lot of sleep.